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Posted By Topic: Industrial submains

Mar 12 2020 00:02

A small industrial building (~4000m2) with a MSB and about 7 or 8 distribution boards of varying sizes (160A/ph was the largest submain).

Most of the DBs also have a separate submain to them for lighting. Some are single phase lighting (20-32A maybe), even though the main power to the DB is 3ph. Some DBs have 3 phase lighting with 20-32A per phase on the submain.

My question(s) is, what was the reason for separating the lighting on each DB back in the old days?
There doesn't seem to be any master lighting control or separate metering for the lighting.

It wouldn't normally be done like that now would it? Just one submain to DBs would be usual these days?

Mar 12 2020 06:54

Where you are commercial buildings used to be metered separately for power and lighting. Many years ago the lighting tariff was removed and building metering was converted when metering was upgraded or alterations were carried out.
They had two sets of submarines and isolation switches at each board. Larger buildings had two panels at each DB.
It can be a trap for unaware sparkies loading up the old lighting panels thinking there's lots of spare spaces

Mar 12 2020 11:13

Thanks for the information Nalla.
At the moment it is setup for day and night rate, as there was night store heaters and I think maybe some underfloor heating. Mostly it seems to be disconnected.
Yes the lighting could have been metered separately at some point I guess. There is a newer DB without a separate lighting submain.